The deadliest form of hepatitis is one you've probably never heard of

May is Hepatitis Awareness Month, and Yahoo Lifestyle will be shining light on the illness, which affects hundreds of millions of people worldwide, with educational articles and first-person accounts.

You’re probably aware that there is more than one form of hepatitis, but it’s understandable if you can’t keep them all straight. After all, there are five main forms of the disease. But while they share the name “hepatitis,” they’re not exactly the same.

“They’re all caused by different viruses, and they all have different prognoses — some can lead to liver cancer, and some don’t,” infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security, tells Yahoo Lifestyle.

At its core, hepatitis is an inflammation of the liver, Carlos Romero-Marrero, MD, a hepatologist at the Cleveland Clinic specializing in hepatitis and liver disease, tells Yahoo Lifestyle. But from there, things are a little more nuanced.

Hepatitis as a whole isn’t overly common in the United States, but cases of viral hepatitis (which includes hepatitis A, B, and C) have been on the rise in recent years, according to data from the Centers for Disease Control and Prevention. “Hepatitis A, B, and C are the biggest hepatitis viruses in the U.S.,” William Schaffner, MD, an infectious disease specialist and professor at the Vanderbilt University School of Medicine, tells Yahoo Lifestyle.

To help you understand the different forms of hepatitis, here’s a breakdown of each type, plus what you need to do to lower your risk of contracting them:

Hepatitis A

Hepatitis A is a contagious liver infection caused by the hepatitis A virus, according to the Mayo Clinic. This form of the disease can be transmitted a few different ways, but you’re most likely to get it after having contaminated food or water, or from being in close contact with a person who is infected, Adalja says. Symptoms usually include fatigue, nausea and vomiting, clay-colored bowel movements, a loss of appetite, jaundice, and itchiness.

It’s possible to have a mild case of hepatitis A, which goes away without treatment, the Mayo Clinic says, and most people who are infected recover within six months with no permanent liver damage. To lower the odds you’ll contract hepatitis A, it’s a good idea to practice good hand hygiene and avoid eating raw shellfish from polluted waters, Adalja says.

Hepatitis B

Hepatitis B is a liver infection that’s caused by the hepatitis B virus. It’s usually either sexually transmitted or contracted when blood infected with the hepatitis B virus enters a person’s body, Adalja says. Hepatitis B can be a short-term infection, but in some people it becomes chronic, the CDC notes. Chronic hepatitis B can lead to cirrhosis (i.e., permanent scarring) of the liver or liver cancer, says Adalja.

Hepatitis B symptoms are similar to those of hepatitis A and include abdominal pain, dark urine, fever, joint pain, loss of appetite, nausea, weakness, and jaundice, says the Mayo Clinic. There is a vaccine to prevent hepatitis B, and it’s usually given to babies shortly after they’re born, according to the CDC. People are most at risk for contracting hepatitis B from sharing needles and having unprotected sex, Romero-Marrero says. Unfortunately, there’s no cure for hepatitis B if you contract it.

Hepatitis C

Hepatitis C is a liver infection caused by the bloodborne hepatitis C virus. Most people are infected with hepatitis C by sharing needles during illicit drug use, Adalja says. However, people who had a blood transfusion before 1990 (when blood wasn’t screened for the hepatitis C virus) are at a higher risk than others of having the infection, Romero-Marrero says.

About half of people with hepatitis C don’t know they have it because they don’t experience symptoms (which can take decades to show up). Symptoms generally include bleeding and bruising easily, fatigue, loss of appetite, jaundice, itchy skin, and fluid buildup in the abdomen, according to the Mayo Clinic.

Hepatitis C can be a short-term illness, but it’s chronic for up to 85 percent of people who contract it, the CDC says — and it can lead to long-term complications like cirrhosis of the liver, liver cancer, and liver failure if it goes untreated. Chronic hepatitis C is usually curable with oral anti-viral medication that’s taken every day for two to six months, the Mayo Clinic says.

Hepatitis D

Hepatitis D is caused by the hepatitis D virus, but it needs hepatitis B to exist, Romero-Marrero points out. The infection is transmitted through contact with an infected person’s blood or bodily fluids, according to the World Health Organization.

People can acquire hepatitis D at the same time they contract hepatitis B or have it as a superinfection with an existing hepatitis B infection, according to the CDC. Symptoms generally include jaundice, fatigue, dark urine, abdominal pain, loss of appetite, vomiting, nausea, and joint pain. People who have hepatitis D are at a higher risk of having more severe symptoms and up to a 20 percent risk of developing acute liver failure compared with those who have only hepatitis B.

There’s no treatment for hepatitis D, the WHO says, but getting the hepatitis B vaccine can prevent it.

Hepatitis E

Hepatitis E is a liver infection caused by the hepatitis E virus. It’s usually spread through fecal-oral contact (in microscopic amounts) and is often transmitted by contaminated water in countries that have bad sanitation, Adalja says. “It isn’t so common in the U.S., but we do get some cases,” he adds.

Symptoms are similar to those of other forms of hepatitis and include fever, fatigue, loss of appetite, vomiting, nausea, stomach pain, jaundice, dark urine, and clay-colored stool, says the CDC. Luckily, most people with hepatitis E recover completely without any treatment.

On the whole, you need not stress out about contracting hepatitis in any form provided you practice safe sex, don’t use IV drugs, and didn’t have a blood transfusion before 1990. But it’s important to be aware that cases can and do show up in the United States, Romero-Marrero points out.

If you’re experiencing symptoms of any form of hepatitis, talk to your doctor — a physician should be able to confirm a diagnosis and recommend a course of action to improve your health.